/**
 * Copyright (c) 2012-2014 Luke Dashjr
 * Copyright (c) 2013-2014 Pavol Rusnak
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
 * OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

#include "base58.h"
#include <stdbool.h>
#include <string.h>
#include "memzero.h"
#include "ripemd160.h"
#include "sha2.h"

const char b58digits_ordered[] = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
const int8_t b58digits_map[] = {
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, 0,  1,  2,  3,  4,  5,  6,  7,  8,  -1, -1, -1, -1, -1, -1, -1, 9,
    10, 11, 12, 13, 14, 15, 16, -1, 17, 18, 19, 20, 21, -1, 22, 23, 24, 25, 26, 27, 28, 29,
    30, 31, 32, -1, -1, -1, -1, -1, -1, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, -1, 44,
    45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, -1, -1, -1, -1, -1,
};

typedef uint64_t b58_maxint_t;
typedef uint32_t b58_almostmaxint_t;
#define b58_almostmaxint_bits (sizeof(b58_almostmaxint_t) * 8)
static const b58_almostmaxint_t b58_almostmaxint_mask =
    ((((b58_maxint_t)1) << b58_almostmaxint_bits) - 1);

// Decodes a null-terminated Base58 string `b58` to binary and writes the result
// at the end of the buffer `bin` of size `*binszp`. On success `*binszp` is set
// to the number of valid bytes at the end of the buffer.
bool b58tobin(void* bin, size_t* binszp, const char* b58) {
    size_t binsz = *binszp;

    if(binsz == 0) {
        return false;
    }

    const unsigned char* b58u = (const unsigned char*)b58;
    unsigned char* binu = bin;
    size_t outisz = (binsz + sizeof(b58_almostmaxint_t) - 1) / sizeof(b58_almostmaxint_t);
    b58_almostmaxint_t outi[outisz];
    b58_maxint_t t = 0;
    b58_almostmaxint_t c = 0;
    size_t i = 0, j = 0;
    uint8_t bytesleft = binsz % sizeof(b58_almostmaxint_t);
    b58_almostmaxint_t zeromask = bytesleft ? (b58_almostmaxint_mask << (bytesleft * 8)) : 0;
    unsigned zerocount = 0;

    size_t b58sz = strlen(b58);

    memzero(outi, sizeof(outi));

    // Leading zeros, just count
    for(i = 0; i < b58sz && b58u[i] == '1'; ++i) ++zerocount;

    for(; i < b58sz; ++i) {
        if(b58u[i] & 0x80)
            // High-bit set on invalid digit
            return false;
        if(b58digits_map[b58u[i]] == -1)
            // Invalid base58 digit
            return false;
        c = (unsigned)b58digits_map[b58u[i]];
        for(j = outisz; j--;) {
            t = ((b58_maxint_t)outi[j]) * 58 + c;
            c = t >> b58_almostmaxint_bits;
            outi[j] = t & b58_almostmaxint_mask;
        }
        if(c)
            // Output number too big (carry to the next int32)
            return false;
        if(outi[0] & zeromask)
            // Output number too big (last int32 filled too far)
            return false;
    }

    j = 0;
    if(bytesleft) {
        for(i = bytesleft; i > 0; --i) {
            *(binu++) = (outi[0] >> (8 * (i - 1))) & 0xff;
        }
        ++j;
    }

    for(; j < outisz; ++j) {
        for(i = sizeof(*outi); i > 0; --i) {
            *(binu++) = (outi[j] >> (8 * (i - 1))) & 0xff;
        }
    }

    // locate the most significant byte
    binu = bin;
    for(i = 0; i < binsz; ++i) {
        if(binu[i]) break;
    }

    // prepend the correct number of null-bytes
    if(zerocount > i) {
        /* result too large */
        return false;
    }
    *binszp = binsz - i + zerocount;

    return true;
}

int b58check(const void* bin, size_t binsz, HasherType hasher_type, const char* base58str) {
    unsigned char buf[32] = {0};
    const uint8_t* binc = bin;
    unsigned i = 0;
    if(binsz < 4) return -4;
    hasher_Raw(hasher_type, bin, binsz - 4, buf);
    if(memcmp(&binc[binsz - 4], buf, 4)) return -1;

    // Check number of zeros is correct AFTER verifying checksum (to avoid
    // possibility of accessing base58str beyond the end)
    for(i = 0; binc[i] == '\0' && base58str[i] == '1'; ++i) {
    } // Just finding the end of zeros, nothing to do in loop
    if(binc[i] == '\0' || base58str[i] == '1') return -3;

    return binc[0];
}

bool b58enc(char* b58, size_t* b58sz, const void* data, size_t binsz) {
    const uint8_t* bin = data;
    int carry = 0;
    size_t i = 0, j = 0, high = 0, zcount = 0;
    size_t size = 0;

    while(zcount < binsz && !bin[zcount]) ++zcount;

    size = (binsz - zcount) * 138 / 100 + 1;
    uint8_t buf[size];
    memzero(buf, size);

    for(i = zcount, high = size - 1; i < binsz; ++i, high = j) {
        for(carry = bin[i], j = size - 1; (j > high) || carry; --j) {
            carry += 256 * buf[j];
            buf[j] = carry % 58;
            carry /= 58;
            if(!j) {
                // Otherwise j wraps to maxint which is > high
                break;
            }
        }
    }

    for(j = 0; j < size && !buf[j]; ++j)
        ;

    if(*b58sz <= zcount + size - j) {
        *b58sz = zcount + size - j + 1;
        return false;
    }

    if(zcount) memset(b58, '1', zcount);
    for(i = zcount; j < size; ++i, ++j) b58[i] = b58digits_ordered[buf[j]];
    b58[i] = '\0';
    *b58sz = i + 1;

    return true;
}

int base58_encode_check(
    const uint8_t* data,
    int datalen,
    HasherType hasher_type,
    char* str,
    int strsize) {
    if(datalen > 128) {
        return 0;
    }
    uint8_t buf[datalen + 32];
    memset(buf, 0, sizeof(buf));
    uint8_t* hash = buf + datalen;
    memcpy(buf, data, datalen);
    hasher_Raw(hasher_type, data, datalen, hash);
    size_t res = strsize;
    bool success = b58enc(str, &res, buf, datalen + 4);
    memzero(buf, sizeof(buf));
    return success ? res : 0;
}

int base58_decode_check(const char* str, HasherType hasher_type, uint8_t* data, int datalen) {
    if(datalen > 128) {
        return 0;
    }
    uint8_t d[datalen + 4];
    memset(d, 0, sizeof(d));
    size_t res = datalen + 4;
    if(b58tobin(d, &res, str) != true) {
        return 0;
    }
    uint8_t* nd = d + datalen + 4 - res;
    if(b58check(nd, res, hasher_type, str) < 0) {
        return 0;
    }
    memcpy(data, nd, res - 4);
    return res - 4;
}
